I'm using three brackets per side.
@Saddletramp and I fabricated a third bracket out of some steel angle for the front. OK4wd advised only two brackets were necessary on the side mounting rail since that's where most of the weight would be located. I think the spacing didn't work out for the 100 series roof rack brackets I had. The two mounts would have been too close together. So we made a third mount for the very front. A rack where you can slide the crossbars around to where you need them is probably the easiest way. Initially, I didn't want to pay $1000 for a rack to mount a $4000 tent. I used load bar feet I already had and purchased alu-cab cross bars. Later, I got a free Dissent roof rack, so moved it to that.
You're more than welcome to come check mine out if you want. I'm in North Scottsdale, just off the 101.
I got mine from Mudrack in California. They were the west coast distributor at the time. I think OK4wd is the main US distributor, but that could've changed.